1. Field of the Invention
The present invention relates generally to musical instruments, and more particularly to a rigid structural member for a stringed musical instrument.
2. Background
The present invention generally relates to acoustic stringed instruments, namely steel string and nylon stringed guitars, acoustic bass guitars, mandolins, ukuleles, and other instruments which utilize kerfing liner for support of the top and back of the instrument. The instruments for which the kerfing is utilized comprise a fretboard (or fingerboard) upon which the strings are fingered with the fingers of a musician's first hand to produce a desired musical tone when the strings are plucked, picked, bowed or otherwise actuated by the musician's second hand. The instrument comprises a sound chamber, or body, in which sound waves generated by the plucked strings are amplified by the vibrations of the materials forming the sound chamber and emitted from the sound chamber.
The sound chamber has a front (also referred to as the soundboard), back, and sides. In general, the strings of these instruments are attached on one end of the string to a headstock of the instrument, which is positioned at the end of the neck extending from the sound chamber, with the opposite end of the string typically attached to a member called the bridge, which is attached to the soundboard. A member called a saddle is typically mounted on the bridge, where the saddle elevates the strings above the soundboard. The sides of the instrument's sound chamber generally comprise an upper bout, a waist, and a lower bout, where the lower bout is the large rounded bottom of the instrument, the upper bout is the smaller, rounded and convex shape at the top. Under the traditional design of acoustic guitars, the shape of the sound chamber is that of a number “8”, with the upper half, i.e., the upper bout, being smaller than the bottom half, i.e., the lower bout. The upper bout and lower bout are separated by the “waist” of the guitar, which is the concave transition between the upper and lower bouts.
For a right handed player, the right hand is typically utilized for bowing, picking, strumming, or otherwise actuating the strings. For the remainder of this description, it will be assumed that the instrument is “right handed”, i.e., built to be played by a right-handed person. However, correlating the description for a left-handed instrument only requires the assumption that the right hand is utilized for fingering the notes and the left hand is utilized for bowing, picking or strumming the strings.
The sides of the instrument may, for purposes of description, be identified with respect to the strings. The treble strings of the instrument are usually on the side of the instrument generally facing downward as the instrument is played, while the bass strings are on the side of the guitar generally facing upward as the instrument is played. Using the strings as a point of reference, the sides of the instrument may be referred to as the treble side and the bass side. With respect to the string orientation described above, the side of the instrument generally facing downward while played is considered as the treble side of the instrument and the side of the instrument facing upward is considered as the bass side of the instrument. The upper bout may therefore may be further described as having a treble side upper bout and a bass side upper bout and, likewise, the lower bout may be further described as having a bass side lower bout and a treble side lower bout.
For the typical right handed player, the upper bout of the instrument is adjacent to the player's left arm, and the lower bout is adjacent to the player's right arm. The left hand is utilized for fingering notes on the fretboard, where the fretboard is disposed on the neck of the instrument. For many stringed instruments, a portion of the fretboard cantilevers over the soundboard. The portion of the fretboard cantilevering over the soundboard is typically referred to as the fretboard extension.
Kerfing liner or “kerfing” is the term applied to flexible strips of wood which are attached, usually with glue, to the inside edge of a wood support structure where a wood face or top member or a wood back or bottom member is attached in full or partial closure of the support structure, typically when the wood support structure is fabricated of relatively thin-walled material. In the usual application, the kerfing will provide additional contact area for providing a gluing surface where a relatively strong bond between the wood members is required. When applied, this strip of wood provides a wider surface to support the face member and/or back member which is attached to the kerfing by glue or other attachment means. Without the support provided by the kerfing there is not enough width on the sides to create a strong enough joint to hold the two thin plates together with glue (or other attachment means), because each plate typically has a thickness of approximately 0.075 to 0.090″. The kerfing typically provides a “seat” or “shelf” of approximately 0.190″ to support the top member and back member.
In one common application, kerfing is utilized for attaching the front and back members of a musical instrument to the sides of the instrument, such as with guitars, mandolins, acoustic bass guitar, or other stringed instrument utilizing a sound chamber as described above.
The top, back and sides of an acoustic guitar typically have a wall thickness of less than 0.120 inches, typically ranging from 0.075 to 0.090 inches. Because of the thin wall thickness, the available gluing surface for attaching the front and back of the guitar to the sides is quite small. To provide greater strength to this joint, the kerfing is attached, usually with glue, to the inside edge of the sides of the guitar which provides additional support and surface area for gluing. This strip of wood is known as “kerfing.” Under the traditional design, the soundboard and sides of the instrument are at a right angle to each other, defining a common edge. This common edge may have a binding material, such a wood, plastic, or other trim, which protects the corner of the soundboard and side from impact damage.
Acoustic stringed instruments, such as guitars, are constructed to physically and sonically vibrate the soundboard by driving various vibration frequencies of the soundboard by means of transferring vibration energy from a plucked string through the saddle and bridge directly into the soundboard which acts as a vibrating plate. Hence the vibrating soundboard creates sound wave energy. Higher frequency (treble) sound waves are produced and emitted directly off the top face of the soundboard. Lower frequencies (bass) are produced by the soundboard vibrating the air inside the guitar body, emitting the lower frequency sound waves through the sound hole. The greater the soundboard vibration, the greater the sound wave energy produced. Secondary but noticeable tonal sound energy waves also come from the vibrating sides and back of the guitar.
Under the traditional design for guitars, the exterior of the sound chamber has been symmetric, where the treble side and bass side are matching. However, over the years, instrument makers have modified the traditional design. One of the most common of these modifications, which results in an asymmetrical sound chamber, has been to fashion a “cut-away” into the treble side of the upper bout and upper portion of the soundboard adjacent to the neck on the treble side to allow the player greater access to the portions of the fretboard adjacent to the body of the guitar. Other modifications have also been made, such as placing the sound hole in a different position than directly under the strings or, as discussed in greater detail below, modifying the normally right-angled edges between the sides, soundboard, and/or back to form a beveled edge. Another known modification is the inclusion of an ergonomic “armrest” or “bevel” (hereinafter, collectively, “bevels”) which may be constructed into the connection of the soundboard and sides, where the bevel comprises a transitional member from the soundboard into the side. The bevel will generally be located on the bass side of the lower bout section of the guitar. Construction of the bevel can be complicated, often requiring substantial modifications in how the soundboard is supported.
Musical instruments which are constructed by attaching the soundboard and back of the instrument to a seat fabricated from kerfing, as described above, utilize a joint which is subject to losing sound energy because it is not as stiff as it might otherwise be constructed. However, increasing stiffness by increasing the width of the kerfing reduces the available area of soundboard for vibration, thus creating a stiffer and less resonant vibrating plate.
In addition to the issues discussed above, the kerfing typically utilized in instrument construction is not easy to work with, requiring additional time for the artisan to build a musical instrument. The existing kerfing has limited flexiblity. Musical instruments generally have many curved surfaces which often have a radius which is too tight to allow the kerfing to bend or conform to the curved surface without breaking. Thus, the artisan is often required to use sections of kerfing to complete the curved surface.